IEEE802.11 standard provides Open System Authentication and Shared Key Authentication as device authentication methods in a wireless LAN (Local Area Network). Open System Authentication prescribes the exchange of authenticated frames among the wireless terminals. However, since all terminals that request authentication are permitted in Open System Authentication, unauthorized access from a malicious third party cannot be blocked by Open System Authentication. Shared Key Authentication prescribes the advance sharing of a passphrase used as a shared key among the wireless terminals, but does not prescribe a sharing method. Generally, a user obtains the shared key notified verbally or distributed by an electronic mail and sets a passphrase used as the shared key on the wireless terminal.
Further, IEEE802.11i standard and WPA (Wi-Fi Protect Access) standard that are intended to strengthen security of a wireless LAN, provide device authentication using an authentication server in RADIUS (Remote Authentication Dial In User Service) or other authentication servers. The wireless terminal that requests authentication sends an authentication request by wireless to a base station connected to the wired network. The base station asks the authentication server included in the wired network by wire communication whether an authentication can be granted or not. For the sake of the authentication of the wireless terminal, terminal information such as a MAC (Media Control Access) address of the wireless terminal that requests authentication must be stored in the authentication server beforehand.
Furthermore, patent document 1 mentioned below discloses the entry of wireless terminal information by wireless communication using a public key cryptosystem.
Moreover, patent document 2 mentioned below discloses a technology for grouping terminals that have the identical common information by sharing the common information and for authenticating the terminals with reference to a group list.
Further, patent document 3 mentioned below discloses a technology for performing the public key authentication in accordance with a MAC address list held by a base station (AP), by using a public key certificate set in each terminal beforehand.
Patent document 1: Japanese Patent Application Kokai (Laid-Open) Publication No. 2002-159053
Patent document 2: Japanese Patent Application Kokai (Laid-Open) Publication No. 2003-198544
Patent document 3: Japanese Patent Application Kokai (Laid-Open) Publication No. 2003-005641